1. Field of the Invention
The present invention is directed to frosting coating materials, coated articles, coating methods, and, in certain particular aspects, to coating methods and materials useful in producing a frosted plastic or glass article.
2. Description of Related Art
A substrate of glass or plastic may become frosted when a surface temperature thereof is heated, e.g. to 355-365 degrees F. and then cooled to room temperature. In certain prior art methods, a frosting coating is provided with, e.g. thermosetting polymers and other chemicals which produce a frosting effect due to moisture adjustment (expulsion) by heating. The prior art discloses a wide variety of systems and methods for coating articles to produce a frosted article. U.S. Pat. Nos. 6,476,093; 6,777,092; 6,641,755; 5,916,938; 6,193,831; U.S. Applications published with numbers 20040049052, 20040058078, and 20040067311; and the references listed in these patents and applications provide a sampling of related art and of frosted articles (e.g. lenses, U.S. Pat. Nos. 5,015,523 and 5,458,820; mirrors and prisms, U.S. Pat. Nos. 4,898,435 and 5,513,039; and optical elements, U.S. Pat. Nos. 6,582,884, 5,933,273, and 5,621,838).
Frosted articles and frosted glass plastic containers are well known and are used for foods, beverages, alcoholic liquors, cosmetics and other materials because they prevent UV transmission and/or improve a design with decoration and an impression of quality or artistry. In many prior art methods, to finish a surface of a glass container so it is frosted, a method is used in which the surface is etched with a hydrofluoric acid solution with added salts such as ammonium fluoride, or a mixed solution of hydrofluoric acid and sulfuric acid with added salts such as ammonium fluoride. Such a method can provide a frosted surface, but the use of a strong acid, such as hydrofluoric acid as an etching agent, can make the handling of agents difficult and can require washing with an acid and water. The treatment of resulting acidic waste water can present problems regarding safety, environment, productivity, and cost.
A method for finishing a surface of a glass container without using such harmful agents includes mixing a fine silica particle as a matting agent into a thermosetting resin or a photocurable resin to form a frosted coating on the surface of the glass container (see, e.g. JP-A 2518/1978 and JP-B 68418/1993); but when such a frosted glass container is immersed into a washing solution such as an aqueous sodium hydroxide solution in a step of alkali washing, the coating can turn white and can peel from the container and, when such a glass container passes through an alkali washing line or a bottling line, cracking and peeling of the coating can occur by collision between bottles due to insufficient impact resistance of the coating.
One attempted solution to these problems disclosed in U.S. Pat. No. 6,476,093 is a frost-coating composition, which includes a hydrophobic silica particle or a polymer particle, in addition to a photocurable compound; and a frosted glass container coated with such a composition.
One such frost-coating composition includes 5-50 parts by weight of a hydrophobic fine silica particle based on 100 parts by weight of a photocurable compound, such that said frost-coating composition forms a frosted coating having alkaline resistance.
Certain coatings of U.S. Pat. No. 6,476,093 include a solvent-based solution with a relatively high VOC content and, in certain manufacturing processes an epoxy polymer solution is heated for a minimum of two hours at one hundred fifty degrees centigrade.
There is a need, recognized by the present inventor, for efficient and effective materials and methods for frosting coatings.
There is a need, recognized by the present inventor, for such frosting coating materials and methods useful for producing a coating with high surface hardness to combat undesirable etching, e.g. acid etching, of an article.